One reason is loose lug nuts, that is really hard on studs. Good idea to check the lug nut length, and thicker washers could help.

I like to use a torque wrench to 100 lb-ft. Then after making the first pass, torque them again. They should stay tight after that. Since I rotate my slicks side to side every 20 passes, this gets done often. Otherwise think about checking them periodically with the torque wrench. Maybe every 3 months. It can't hurt to check them at the beginning of each race day if you are having problems with them coming loose.